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New World Screwworm Is Close

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Commentary by Bill Bullard, CEO, R-CALF USA

Effective November 22, the U.S. Department of Agricultureโ€™s veterinary agency, the Animal and Plant Health Inspection Service (APHIS) temporarily suspended the importation of cattle from Mexico. This was APHISโ€™ response to a recent notification that Mexico had detected a cow with new world screwworm in southern Mexico.  

The new world screwworm is a fly, and more specifically, it is the flyโ€™s larvae that emerges from an egg the fly lays in an animalโ€™s open wound. There the larvae emerges from its egg and begins eating the live flesh of the animal. If untreated, the hatching larvae may cause a parasitic infection on and under the skin and can lead to death. New world screwworm can infect wildlife, livestock, pets, and more rarely, humans.

The new world screwworm thrives in subtropical and tropical climates and is endemic in South America, such as in Guatemala, Honduras, Costa Rica, Argentina, Brazil, and Uruguay, just to name a few countries where it is known to exist. However, whether carried by storms or animals, the fly has occasionally reached northward to Mexico and the United States.

The United States experienced outbreaks of new world screwworm in Florida and Texas during the late 50s and mid-60s, respectively, and the U.S. spent hundreds of millions of dollars in eradication efforts through 1982, which was the year the new world screwworm was considered eradicated from the United States. However, reports submitted to the World Organization for Animal Health indicate isolated detections in Florida in 2016 and 2017. The method deployed to eradicate the fly involved release of millions of sterilized male flies.   

APHISโ€™ regulations recognize the health and economic dangers from this foreign animal pest, and they prescribe mitigation measures for the importation of susceptible animals from the list of regions where new world screwworm is known to exist. But Mexico, where the new world screwworm was recently detected, was not on this list, but now it is.  

So now that APHIS has added Mexico to the list of affected countries and has suspended the importation of cattle and bison from Mexico, in order for the agency to resume such importation, it must first reassess Mexicoโ€™s disease status in a notice the agency must publish in the Federal Register, and the public may comment on this notice.

If APHIS makes a determination that the importation of cattle from Mexico should be resumed, the public will be afforded the opportunity to comment on that determination, and cattle from Mexico would likely be subjected to APHISโ€™ new world screwworm mitigations, which include treating all cattle with ivermectin 3-5 days before importation, treating all open wounds with a livestock dust insecticide, and certifying all livestock as pest-free by a veterinarian.

Because many of the larger feedlots in the South and larger beef packers rely on the over one million cattle imported each year from Mexico, we expect there to be a rather loud cry from the industry to โ€œnormalizeโ€ trade with Mexico as quickly as possible, even despite the risk of introducing new world screwworm into the U.S. cattle herd.

But hereโ€™s what we need to watch for: Just before the elections, the Wildlife Conservation Society published an article titled, โ€œCattle trafficking routes: The screwworm’s gateway to Mexico.”

That article reported on recent studies conducted by specialists at the National Autonomous University of Mexico. Those studies indicate that illegal cattle trafficking from South American countries northward were likely fueling the accelerated spread of the new world screwworm.

The article quotes the researchers as stating, โ€˜If the spread is allowed to advance unchecked, it is highly likely to follow the cattle trafficking route through Guatemalaโ€™s Maya Biosphere Reserve and into Mexico.โ€™

And the article further states: 

โ€œOnce the screwworm crosses the border, controlling its spread within Mexican territory will be challenging. Past experiences have demonstrated the complexity and cost of eradicating this pest; efforts in Mexico and the U.S. in 1991 exceeded $955 million in todayโ€™s currency.โ€ 

What this information tells us is that we have a very serious threat of an introduction of a very serious foreign animal pest that has already spread to Mexico from South America, likely through illegal cattle trafficking. 

Regulations alone canโ€™t fix unlawful cattle trafficking so we must remain vigilant to ensure that APHIS does not prematurely โ€œnormalizeโ€ trade with Mexico before both the problem and the cause of the problem is solved.

This could be dรฉjร  vu all over again as youโ€™ll recall it was R-CALF USA that challenged APHIS in a years-long lawsuit in the 2000s when the agency tried to โ€œnormalizeโ€ trade with Canada while Canada continued to experience outbreaks of bovine spongiform encephalopathy (BSE).